Issue #10332: multiprocessing: fix a race condition when a Pool is closed
before all tasks have completed.
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index c66876a..bcbf7e3 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -294,7 +294,11 @@
@staticmethod
def _handle_workers(pool):
- while pool._worker_handler._state == RUN and pool._state == RUN:
+ thread = threading.current_thread()
+
+ # Keep maintaining workers until the cache gets drained, unless the pool
+ # is terminated.
+ while thread._state == RUN or (pool._cache and thread._state != TERMINATE):
pool._maintain_pool()
time.sleep(0.1)
# send sentinel to stop workers
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 201fa98..14847d9 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1168,6 +1168,20 @@
p.close()
p.join()
+ def test_pool_worker_lifetime_early_close(self):
+ # Issue #10332: closing a pool whose workers have limited lifetimes
+ # before all the tasks completed would make join() hang.
+ p = multiprocessing.Pool(3, maxtasksperchild=1)
+ results = []
+ for i in range(6):
+ results.append(p.apply_async(sqr, (i, 0.3)))
+ p.close()
+ p.join()
+ # check the results
+ for (j, res) in enumerate(results):
+ self.assertEqual(res.get(), sqr(j))
+
+
#
# Test that manager has expected number of shared objects left
#
diff --git a/Misc/NEWS b/Misc/NEWS
index a501954..10daf5b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -66,6 +66,9 @@
Library
-------
+- Issue #10332: multiprocessing: fix a race condition when a Pool is closed
+ before all tasks have completed.
+
- Issue #1548891: The cStringIO.StringIO() constructor now encodes unicode
arguments with the system default encoding just like the write() method
does, instead of converting it to a raw buffer. This also fixes handling of